As examples of storage devices included in general host systems such as computer systems, there are magnetic hard disk drives (HDD), solid state drives (SSD) having nonvolatile semiconductor memories such as NAND flash memory mounted thereon, and embedded NAND flash memory. SSDs and embedded NAND flash memory are classified as storages, but can also be described as memory systems with extended sizes.
Such a memory system includes an interface, a first memory block, a second memory block and a controller, for example. The first memory block stores data, and the second memory block is a buffer memory for writing/reading data.
Description will be given considering an SSD as a system of the related art. Herein, an SSD refers to a storage constituted by NAND flash-based solid-state memory in a broad sense and also includes a NAND flash memory embedded system. Since writing to NAND flash memory is performed in units of a page, there is a disadvantage that a large number of data write requests in smaller units (requests to write data smaller than a page size) results in many empty areas in the NAND flash memory and thus results in decrease in the use efficiency.